The following relates generally to wireless communication, and more specifically to low latency (LL) with time division duplexing (TDD) carrier configurations.
Wireless communications systems are widely deployed to provide various types of communication content such as voice, video, packet data, messaging, broadcast, and so on. These systems may be multiple-access systems capable of supporting communication with multiple users by sharing the available system resources (e.g., time, frequency, and power). Examples of such multiple-access systems include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, and orthogonal frequency division multiple access (OFDMA) systems, (e.g., a Long Term Evolution (LTE) system).
By way of example, a wireless multiple-access communications system may include a number of base stations, each simultaneously supporting communication for multiple communication devices, which may be otherwise known as user equipment (UEs). A base station may communicate with the communication devices on downlink channels (e.g., for transmissions from a base station to a UE) and uplink channels (e.g., for transmissions from a UE to a base station).
A wireless communication system may implement a feedback scheme to increase the reliability and robustness of transmissions between two devices. For instance, a receiving device may receive a signal from a transmitting device and send information regarding the condition of the received signal back to the transmitting device (e.g., an acknowledgement/negative acknowledgement (ACK/NACK)). The transmitting device may use the feedback information to determine the content of subsequent transmissions; for instance, the transmitting device may resend a signal that arrived at the receiving device with errors and it receives a NACK. The transmitting device may wait until it receives the ACK/NACK feedback before transmitting or retransmitting information. A longer transmission time interval (TTI) structure may result in higher latency between transmissions or retransmissions than may be realized in systems having shorter TTI structures. In some applications, such as voice calls, streaming media, or gaming, latency may decrease system performance and negatively impact user experience.